Draw roll



Feb. 13, 1962 United States Patent Gfiice 3,020,621 Patented Feb. 13,1962 3,020,621 DRAW ROLL David Sacks, Seaford, Del., assignor to E. I.du Pont de Nemours and Company, Wilmington, Del., a corporation ofDelaware Filed Dec. 3, 1959, Ser. No. 857,077 5 Claims. (Cl. 28-71.3)

This invention relates generally to the production of filamentarystructures such as yarn or thread. More particularly, it has to do withthe apparatus which is used in advancing such filamentary structuresthrough a process.

In many processes, it is customary to advance the filamentary structurefrom step to step by means of rolls. For example, where the structure isbeing drawn, two rolls are employed and have their axes skewed so that ap-lurality of wraps will remain separated on the roll surfaces. Thefilamentary structure may be either a monofilament, a multifilament yarnor thread, a yarn bundle, or the like. Both rolls may be driven insynchronism or one roll may be driven and the other an idler. In theseprocesses, individual filaments frequently pull out of the structure andwrap on one of the rolls. These filament back-wraps degrade theprocessed yarn and may even build up to such an extent as to completelybreak down the threadline. In a conventional drawing process, draw rollwraps are one of the major causes of equipment out time.

It is known that the number of process interruptions due to filamentwraps may be reduced by providing a low friction finish on the rolls.However, with the use of such a finish, it is required that more wrapsor turns of the yarn about the roll assembly be taken than where highfriction rolls are employed. Thus, a low friction finish necessitatesthe use of longer rolls which may result in a yarn storage time notconsistent with the process or in difiiculties having to do with thelocation of the longer rolls in existing equipment. Obviously, more timeis consumed in the string-up of longer, low friction rolls since morewraps are required.

The general objective of the present invention is the provision of anassembly of rolls which, because of their special characteristics,substantially reduce the incidence of draw roll wraps and, at the sametime, require no elongation of or excessive number of turns about therolls.

The most important object of the present invention is to provide a drawroll having alternate low and high friction finishes on the surfacethereof.

A further object of the invention is the provision of a draw roll havinga low friction finish in those sections where there is either tangentialor radial motion or any combination thereof between the yarn and theroll and a relatively high friction finish at some intermediate sectionof the roll.

With these "and other objects in view, the draw roll assembly of theinvention includes a pair of cylindrical dra-w rolls having their axesspaced and skewed, with either or both of the rolls having a highfriction finish on an intermediate section and a comparatively lowfriction finish on the end sections.

Other objectives will become apparent in the following specificationwherein reference is made to the accompanying drawing. The single figureis a side view of a preferred embodiment of the draw roll assembly ofthe present invention.

The illustrated draw roll assembly is intended for use in an apparatusof the type disclosed in U.S. Patent No. 2,289,232 and includes a drawroll 10 as well as a separator roll 12. Cylindrical rolls 10, 12 are onthe ends of shafts 14, 16, respectively, and have their axes skewed.Shaft 14 is driven whereas shaft 16 is an idler brought to speed by afilamentary yarn end 18 which passes over the rolls. The cylindricalsurface of roll 10 is divided into at least three sections 20, 22, 24.The surfaces of roll 12 and end sections 20, 24 of roll 10 have arelatively low friction finish whereas the surface of intermediatesection 22 is provided with a high friction finish. A finish of thelatter type, which is suitable for use on a draw roll, is a highlypolished chrome plate or mirror finish having a coefiicient of frictionrelative to synthetic polyamide fibers exceeding 0.25. An elastomericmaterial such as rubber could also be used in fabricating the highfriction surface of roll 10. A typical low friction finish is applied bysuccessively sand blasting and chrome plating surface sections 20, 24.Such a matte finish has a coefiicient of friction relative to syntheticpolyamide fibers in the order of 0.14.

In operation, the draw r'oll assembly is strung-up with a suitable handtool such as the aspirator device disclosed by Miller in U.S. Patent No.2,667,964. On string-up of a running high friction roll, individualfilaments are often pulled from the yarn bundle at the point where theyarn is moving both tangentially and radially with respect to the rolland is accelerated by its gripping contact with the roll. The provisionof a low friction finish on section 20 permits the yarn to slip duringplacement of the initial wraps. The yarn next passes to section 22 whichhas a high friction finish and thus acts to grip the yarn and maintainyarn speed at roll surface speed. Sections 20, 22 thus coact to permit agradual acceleration of the running yarn from the speed at which ittravels through the string-up device to roll speed. Similarly, theprovision of a low friction finish on section 24 prevents individualfilaments of the yarn from clinging to the roll surface in the take-offarea.

In the illustrated embodiment, only draw roll 10 has been described asprovided with a multi-tone finish. Under some process conditions, e.g.,where both rolls are driven, it is also desirable to provide both highand low friction surfaces on the roll 12.

The features disclosed herein have special utility in any yarn processrequiring live" string-up of running rolls. The number of differentZones is not limited to three and any greater number may be employed asrequired by specific applications. It should also be noted that the lineof demarcation between the zones need not be a straight line but may beirregular. The general principle must be followed, however, by providinglow frictional characteristics wherever relative movement of the yarnwith respeot to the roll surface either tangential or radial exists oris desired and by providing surfaces having high frictionalcharacteristics where no such relative movement exists so as to takeadvantage of maximum pulling power with a minimum number of roll wraps.

I claim:

1. A draw roll assembly comprising a pair of cylindrical draw rollshaving their axes spaced and skewed, one

of said rolls having a rigid inelastic high friction surface on at leastone section intermediate its ends and a rigid inelastic comparativelylow friction surface on the end sections thereof, said sections havingsubstantially equal diameters.

2. The assembly of claim 1 wherein said high and low friction surfaceshave mirror and matte finishes, respectively.

3. The assembly of claim 2 wherein the other of said rolls also isprovided with a matte finish.

4. As an article of manufacture, a draw roll having a rigid, cylindricalsurface provided with a high friction finish on an intermediate sectionand a comparatively low friction finish on the end sections thereof, thehigh fric- References Cited in the file of this patent UNITED STATESPATENTS 2,173,001 Jordan et a1. Sept. 12, 1939 2,389,878 Symmes Nov. 27,1945 2,588,420 Shaw Mar. 11, 1952

